I. Field of the Invention
The present invention relates to conveyors such as augers and other screw conveyors. More specifically, this invention relates to an improved design for the flighting of such conveyors and the equipment and methods used to make such flighting.
Screw conveyors are one of several inventions and discoveries traditionally attributed to Archimedes in the Third Century B.C. Such conveyors comprise a screw inside a hollow pipe or tube. The screw has a shaft and flighting surrounding the shaft. As the screw turns inside the tube, material is carried by the flighting from one end of the tube to the other. Such material can be a liquid such as water or other aggregate materials such as grain.
Efforts have been made since the earliest invention of the screw conveyor to improve on the basic invention. Some of these efforts relate to trying to improve the capacity of the screw conveyor by, for example, changing the diameter of the tube and changing the number and angle of the flights. Other efforts have been made to improve the life span of the conveyor which is susceptible to substantial wear especially at the outside peripheral edge of the flighting. In the more than 2300 years since the screw conveyor was first invented, no one has been able to satisfactorily modify the basic design to improve the capacity of the conveyor and reduce wear at the outside peripheral edge of the flighting.
Historically, the shaft and flighting of a screw conveyor have been integrally formed. More commonly, however, the flighting and shaft are separately formed and then joined together by a weldment. A cold rolling process is typically used to form the flighting.
The cold rolling process traditionally used has resulted in a helical flighting having an inner edge nearest the shaft which is thicker than the outside peripheral edge nearest the tube surrounding the screw. The outside peripheral edge has traditionally been the portion most subject to wear because of frictional forces between the tube, the material being conveyed and the flighting.
Various attempts have been made to improve the wear characteristics of flighting by increasing the thickness of the outside peripheral edge. For example, U.S. Pat. No. 1,113,688 to G. M. Porter dated Oct. 13, 1914 discloses several embodiments in which auxiliary helical members are secured to the flighting to augment the thickness of the outside peripheral edge of the flighting for improved wear characteristics. U.S. Pat. No. 1,684,254 to J. O. Bailey dated Apr. 26, 1927 discloses several embodiments including a peripheral bead or thickened portion 7 on the outside peripheral edge of the flighting. Adding auxiliary helical members as disclosed in the Porter patent or beading as disclosed in the Bailey patent increases the time, expense and number of steps required to complete construction of the flighting. Also, these additional efforts have been of marginal utility because, for example, the abrupt edges, points, and transitions of the beading shown in Bailey and the auxiliary members and thin areas near the auger shaft of Porter are subject to wear and the result is still not long lasting flighting.
U.S. Pat. No. 5,678,440 to Hamilton represents an effort to provide beading similar to that disclosed in Bailey without requiring additional steps, time, or money. However, the flighting disclosed in the Hamilton patent, shown herein in FIG. 2, is subject to unacceptable wear. Such wear is particularly acute in the area of the sharp radius on the carrying side of the flighting where the flighting transitions from a thinner area to the thicker area adjacent the outside edge of the flighting.
II. Related Art